Oker Dam
Encyclopedia
The Oker Dam is a dam
in the Harz mountains in Lower Saxony
, Germany
. It is fed by the River Oker
.
is in the shape of an arch (see arch-gravity dam
). It is 75 m high, 260 m long, can impound up to 47 million m³ of water
and provides hydropower
, flood protection and water regulation at times of low water. It is also used indirectly for the production of drinking water
. Its average annual discharge is 75 million m³. The hydro-electric power station at Romkerhalle is fed by the Oker Reservoir.
and Brunswick
in the winter of 1946/47 when there were heavy falls of snow. Before work started the small hamlet of Schulenberg in the valley had to be abandoned; it was rebuilt above the reservoir.
The Oker Reservoir lies alongside the B 498 federal road, that follows the course of the River Oker between Goslar
and Altenau. On the east bank is a forest road, that is out of bounds to private vehicles.
With its many side arms the Oker Reservoir resembles the much larger Bigge Reservoir in the Sauerland
in west Germany. For the same reason it is also known as the "Vierwaldstättersee of the Harz".
). There are numerous restaurants and cafés along the road. In very calm conditions (no wind or precipitation and no man-made disturbances) a very flat surface forms on the reservoir which mirrors clearly the surrounding landscape.
(max. 15 m of water at the pre-dam) in order to create a wetland
in the Kellwasser valley. Only when there is a very high level of water in the Oker Reservoir are both reservoirs at the same height. The water level in the pre-dam lake can even rise a few decimetres higher.
. It has a descent of 80 m, the nominal discharge is 6.5 m³ per second and it generates 12.5 million kWh per year. The power station is operated as a peaking power plant
working for about 8 hours per day. It discharges directly into the river bed of the Oker. At this point the whitewater
section of the Oker begins and is especially popular with canoeists. Large and sometimes abrupt changes in water level on the Oker result from the unregulated flow of the power station from here as far as the stilling basin of the Oker Reservoir. The Romkerhalle power station is also called the Oker Hydro-Electric Power Station (Wasserkraftwerk Oker).
from Altenau
and Schulenberg
is led away in a separate pipe around the Oker Reservoir to the Goslar-Oker sewage farm
.
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...
in the Harz mountains in Lower Saxony
Lower Saxony
Lower Saxony is a German state situated in north-western Germany and is second in area and fourth in population among the sixteen states of Germany...
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. It is fed by the River Oker
Oker
The Oker is a river in Lower Saxony, Germany, that has historically formed an important political boundary. It is a left tributary of the River Aller, in length and runs in a generally northerly direction.- Course :...
.
Technology
The damDam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...
is in the shape of an arch (see arch-gravity dam
Arch-gravity dam
An arch-gravity dam, curved-gravity dam or arched dam is a dam with the characteristics of both an arch dam and a gravity dam. It is a dam that curves upstream in a narrowing curve that directs most of the water against the canyon rock walls, providing the force to compress the dam...
). It is 75 m high, 260 m long, can impound up to 47 million m³ of water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
and provides hydropower
Hydropower
Hydropower, hydraulic power, hydrokinetic power or water power is power that is derived from the force or energy of falling water, which may be harnessed for useful purposes. Since ancient times, hydropower has been used for irrigation and the operation of various mechanical devices, such as...
, flood protection and water regulation at times of low water. It is also used indirectly for the production of drinking water
Drinking water
Drinking water or potable water is water pure enough to be consumed or used with low risk of immediate or long term harm. In most developed countries, the water supplied to households, commerce and industry is all of drinking water standard, even though only a very small proportion is actually...
. Its average annual discharge is 75 million m³. The hydro-electric power station at Romkerhalle is fed by the Oker Reservoir.
History and location
The construction of the Oker Dam was begun by Hr. Press in the years 1938 to 1942 and then completed between 1949 and 1956. Its completion became pressing following the devastating floods in WolfenbüttelWolfenbüttel
Wolfenbüttel is a town in Lower Saxony, Germany, located on the Oker river about 13 kilometres south of Brunswick. It is the seat of the District of Wolfenbüttel and of the bishop of the Protestant Lutheran State Church of Brunswick...
and Brunswick
Braunschweig
Braunschweig , is a city of 247,400 people, located in the federal-state of Lower Saxony, Germany. It is located north of the Harz mountains at the farthest navigable point of the Oker river, which connects to the North Sea via the rivers Aller and Weser....
in the winter of 1946/47 when there were heavy falls of snow. Before work started the small hamlet of Schulenberg in the valley had to be abandoned; it was rebuilt above the reservoir.
The Oker Reservoir lies alongside the B 498 federal road, that follows the course of the River Oker between Goslar
Goslar
Goslar is a historic town in Lower Saxony, Germany. It is the administrative centre of the district of Goslar and located on the northwestern slopes of the Harz mountain range. The Old Town of Goslar and the Mines of Rammelsberg are UNESCO World Heritage Sites.-Geography:Goslar is situated at the...
and Altenau. On the east bank is a forest road, that is out of bounds to private vehicles.
With its many side arms the Oker Reservoir resembles the much larger Bigge Reservoir in the Sauerland
Sauerland
The Sauerland is a rural, hilly area spreading across most of the south-eastern part of North Rhine-Westphalia, in parts heavily forested and, apart from the major valleys, sparsely inhabited...
in west Germany. For the same reason it is also known as the "Vierwaldstättersee of the Harz".
Tourism
From the beginning of March to the beginning of January a passenger boat plies the reservoir ferrying tourists (only at weekends during the off-peak seasons). This boat service is the highest (above sea level in Lower Saxony. In addition, during the summer months, numerous, private, unmotorised water craft grace the waters of the reservoir. Swimming and diving are also permitted, apart from certain out-of-bounds areas such as the zone near the dam wall. In winter, when the ice is not thick enough to support weight, ice swimming takes place. There is a circular route, using roads and paths, around the Oker Reservoir which is accessible to unmotorised vehicles or walkers. Between the pre-dam and the primary dam there is a fully metalled circular path, which is used by cyclists, inline skaters and roller skiers. Only the path between the pre-dam and Altenau, which is barred to motor vehicles, is not metalled, but is surfaced with gravel and stone. On the B 498 in summer there is heavy motorcycle traffic (on the northern approach to TorfhausTorfhaus
Torfhaus is a village in the borough of the mining town of Altenau in the Harz mountains of Germany and lies at a height of about .This small settlement consists mainly of restaurants, youth hostels, ski huts and large car parks. It is the highest settlement in Lower Saxony...
). There are numerous restaurants and cafés along the road. In very calm conditions (no wind or precipitation and no man-made disturbances) a very flat surface forms on the reservoir which mirrors clearly the surrounding landscape.
Pre-Dam
The pre-dam (Vorsperre) of the Oker Reservoir is of the gravity dam type, with a height of 20.0 metres. The pre-dam can impound up to 520,000 m³ of water and its primary purpose is to control the water level and cleanliness of the Oker Reservoir. The dam site was designed as a retention basinRetention basin
A retention basin is used to manage stormwater runoff to prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay. Sometimes called a wet pond or wet detention basin, it is an artificial lake with vegetation around the perimeter, and includes a...
(max. 15 m of water at the pre-dam) in order to create a wetland
Wetland
A wetland is an area of land whose soil is saturated with water either permanently or seasonally. Wetlands are categorised by their characteristic vegetation, which is adapted to these unique soil conditions....
in the Kellwasser valley. Only when there is a very high level of water in the Oker Reservoir are both reservoirs at the same height. The water level in the pre-dam lake can even rise a few decimetres higher.
Romkerhalle Hydro-electric Power Station
The hydro-electric power station in Romkerhalle is fed via a pipe from the Oker Reservoir and has a capacity when completed of 4.14 MW. It was opened in 1956 and is equipped with a single Francis turbineFrancis turbine
The Francis turbine is a type of water turbine that was developed by James B. Francis in Lowell, Massachusetts. It is an inward-flow reaction turbine that combines radial and axial flow concepts....
. It has a descent of 80 m, the nominal discharge is 6.5 m³ per second and it generates 12.5 million kWh per year. The power station is operated as a peaking power plant
Peaking power plant
Peaking power plants, also known as peaker plants, and occasionally just "peakers," are power plants that generally run only when there is a high demand, known as peak demand, for electricity.-Peak hours:...
working for about 8 hours per day. It discharges directly into the river bed of the Oker. At this point the whitewater
Whitewater
Whitewater is formed in a rapid, when a river's gradient increases enough to disturb its laminar flow and create turbulence, i.e. form a bubbly, or aerated and unstable current; the frothy water appears white...
section of the Oker begins and is especially popular with canoeists. Large and sometimes abrupt changes in water level on the Oker result from the unregulated flow of the power station from here as far as the stilling basin of the Oker Reservoir. The Romkerhalle power station is also called the Oker Hydro-Electric Power Station (Wasserkraftwerk Oker).
Oker-Grane Tunnel
The 7.4 km long Oker-Grane Tunnel, with its intake near Romkerhalle and outlet on the eastern shore of the Grane Reservoir, conducts water from the Oker Reservoir (power station or bottom outlet) into the Grane Reservoir where it can be purified for use as drinking water. The Grane Reservoir itself only has a relatively small catchment area and is reliant on other tributaries in order to be able to supply drinking water. The Oker-Grane Tunnel was built in the period from 1968 to 1970.Stilling basin
The stilling basin lies about 3 km below the dam of the Oker Reservoir and about 2 km below the Romkerhalle power station. It is furnished with a gravity dam which has a height of 18 metres. The stilling basin can store up to 204,000 m³ of water and its main purpose is to regulate the water level downstream. There is no power station immediately below the dam wall, however it services several smaller power station on the Oker as far as the northern edge of the Harz. Like the Oker Reservoir, in calm weather conditions, it forms a very smooth water surface which reflects the surrounding countryside very clearly. Because of the sheltered location of the stilling basin, this phenomenon occurs very frequently.Sewage
In order not to pollute the water in the reservoir unnecessarily, sewageSewage
Sewage is water-carried waste, in solution or suspension, that is intended to be removed from a community. Also known as wastewater, it is more than 99% water and is characterized by volume or rate of flow, physical condition, chemical constituents and the bacteriological organisms that it contains...
from Altenau
Altenau (Oker)
The Altenau is a small river that rises in the Elm in central Germany, northeast of Eitzum and discharges from the right into the Oker near Halchter, a district of Wolfenbüttel.- Altenau valley :...
and Schulenberg
Schulenberg im Oberharz
Schulenberg im Oberharz is a municipality in the district of Goslar in Lower Saxony, Germany....
is led away in a separate pipe around the Oker Reservoir to the Goslar-Oker sewage farm
Sewage farm
Sewage farms comprise agricultural land irrigated and fertilised with sewage.A precursor to modern sewage treatment systems, household sewage was collected from towns and cities and transported to nearby farm lands. During the middle ages this was accomplished with hand-carried buckets, but as...
.
External links
- Harz waterworks (with current dam data)
- Harz-Life: The Oker Dam